Light emitting device with ceramic conversion material

ABSTRACT

The invention relates to a light delivery device comprising a conversion element and one or several LEDs, which emit light into the conversion element. The light is then converted and emitted with a high radiant flux.

This application claims the benefit or priority of and describes relationships between the following applications: wherein this application is a divisional of U.S. patent application Ser. No. 12/298,047, filed Oct. 22, 2008, which is the National Stage of International Application No. PCT/IB2007/051352, filed Apr. 16, 2007, which claims the priority of foreign application EP06113294.0 filed Apr. 26, 2006, all of which are incorporated herein in whole by reference.

This invention relates to the field of light delivery devices, especially light delivery devices which are used for medical purposes, such as endoscopy.

In endoscopy devices, light is delivered to a body lumen or body cavity, e.g. for diagnostic purposes as well as photodynamic therapy of atherosclerosis, malignant or benign tumor tissue, cancerous cells and other medical treatments. Devices of the prior art are disclosed in e.g. the US 2005/0165462, which is incorporated herein by reference.

Especially in endoscopy devices, which are used for diagnosis, a light source with a high flux density is used, such as Xenon lamps and halogen lamps. However, in prior art applications there is no possibility to change the color temperature of the light without deterioration of the light flux and/or light density. The term ‘color temperature’ is used in lieu of the definition of the correlated color temperature of a light source.

For example in halogen lamps it is possible to decrease the color temperature (increase the red emission relative to green and blue) by simply diminishing the light flux, but a shift towards the red while maintaining the light flux is impossible.

Such a change in color temperature on the other hand would allow a further facilitation of the diagnosis since it is known that e.g. by changing the color temperature the different tissues inside a patient's body, which is subjected to the endoscopy, appear differently on the picture made by the endoscopy camera. Therefore, it would be possible to improve the diagnosis by simply changing the color temperature and/or the spectral composition of the illumination.

It is therefore an object of the present invention to provide a light delivery device, especially a light delivery device for medical purposes, which allows a change in color temperature while essentially maintaining or even improving the light flux and/or light density.

This object is achieved by a light-emitting device having the features of Claim 1. Accordingly, a light delivery device, especially for medical lighting purposes, is provided comprising at least one light emitting device comprising at least one first LED which emits light in the wavelength range of ≧220 nm to ≦550 nm and at least one conversion element placed towards the at least one first LED, which converts at least partly the light from the at least one first LED to light in the wavelength range of ≧300 nm to ≦1000 nm, where the at least one conversion element comprises a ceramic conversion material.

By doing so, it is possible to realize a light delivery device which for most applications in the present invention has one or more of the following advantages:

-   -   Due to the ceramic conversion material, a high light flux         density can be achieved, allowing the use of the light delivery         device in a broad variety of applications, especially for         endoscopical devices     -   Due to the ceramic conversion material it is possible to change         the color temperature of the light delivery device especially         towards the “red” without a deterioration in light flux.     -   Due to the ceramic conversion material it is possible to         increase the light flux without changing the geometrical         properties of light generation and emission, maintaining the         efficiency of any light collection optics.

According to the invention, the light-emitting device comprises at least one first LED which emits light in the wavelength range of ≧220 nm and ≦1000 nm. LEDs with an emittance in this wavelength range have proven themselves in practice.

Preferably, those LEDs consist of a AlInGaN electroluminescent device with a phosphor conversion element attached, absorbing at least partially LED emitted light and reemit that light at a wavelength larger than the LED emission wavelength.

According to a preferred embodiment of the present invention, the light emitting device comprises at least one first LED which emits light in the wavelength range of ≧250 nm and ≦800 nm, more preferably ≧300 nm and ≦780 nm.

The term “ceramic material” in the sense of the present invention means especially a crystalline or polycrystalline compact material or composite material with a controlled amount of pores or which is porefree.

The term “polycrystalline material” in the sense of the present invention means especially a material with a volume density larger than 90 percent of the main constituent, consisting of more than 80 percent of single crystal domains, with each domain being larger than 0.5 μm in diameter and having different crystallographic orientations. The single crystal domains may be connected by amorphous or glassy material or by additional crystalline constituents.

According to a preferred embodiment of the present invention, the at least one conversion element has a refractive index n of ≧1.5 and ≦3 and the ratio A:E is ≧2:1 and ≦50000:1, where A and E are defined as follows:

-   -   the at least one conversion element comprises at least one         entrance surface where light emitted by the at least one LED can         enter the conversion element, and at least one exit surface,         where light can exit the at least one conversion element,     -   each of the at least one entrance surfaces having an entrance         surface area, the entrance surface area(s) being numbered A₁ . .         . A_(n) and each of the at least one exit surfaces having an         exit surface area, the exit surface area(s) being numbered E₁ .         . . E_(n) and the sum of each of the at least one entrance         surface areas A being A=A₁+A₂ . . . +A_(n) and the sum of each         of the at least one exit surface areas E being E=E₁+E₂ . . .         +E_(n)

By doing so, it is possible for most applications within the present invention to realize a lamp combining a high light flux with a greatly increased luminance compared to the LED.

According to a preferred embodiment of the invention, the light emitting device comprises at least one conversion element which comprises at least one entrance surface A where light emitted by the at least one LED can enter the conversion element. After absorption, light reemitted by the conversion element can leave through the entrance surface only with the fraction emitted within the escape cone of the material. The main fraction of the emitted light will be trapped within the conversion element and guided to an exit surface by total internal reflection.

In order to enhance this process, this at least one entrance surface has according to a preferred embodiment of the present invention a roughness Ra of ≧1 nm and ≦500 nm, preferably ≧10 nm and ≦100 nm and more preferably ≧20 nm and ≦40 nm. By this effect it is possible indeed to concentrate light at the exit surface E of the light conversion element.

According to a preferred embodiment of the present invention, the LEDs are in direct contact with the conversion elements but each have a lower refractive index than the conversion elements.

However, according to another preferred embodiment of the present invention, the LEDs and the conversion elements are placed at a distance from each other. In this case, preferably, the distance between the conversion elements and the LEDs is ≧1 μm and ≦100 mm, preferably ≧100 μm and ≦10 mm and more preferably ≧1 mm and ≦5 mm.

Besides the optical function of the separation of the LEDs and the conversion layer it is also advantageous and, insofar a further preferred embodiment of the present invention is concerned, to have a thermal decoupling of the conversion layer and the LEDs. In most applications, the efficiency of the conversion process decreases significantly for temperatures well above 100° C. In another preferred embodiment of this invention special cooling means are applied to the light-emitting device to dissipate heat generated within the conversion layer and the LED(s) to a heat sink outside the device, the LED(s) and the conversion element(s) being placed at a distance from each other preferably as described above. This cooling can be realized by forced air blowing and/or by liquid cooling, pumping a liquid around the conversion layer. In this preferred embodiment of the present invention the cooling means is therefore a liquid, preferably selected from a group comprising Water-, Oils, Propylene-, Ethylene-, Glycol based systems and mixtures thereof. In the latter case the refractive index of the liquid should be as low as possible to prevent light extraction of emitted light through the surface A of the conversion layer. The difference of the refractive index of the conversion layer n_(c) and the liquid n_(l) should be 0.1≦n_(c)−n_(l)≦3, preferably 0.3≦n_(c)−n_(l)≦2.5 and more preferably 0.5≦n_(c)−n_(l)≦2.

According to the invention, the light that enters the conversion element is at least partly converted to light in the wavelength range of ≧300 nm and ≦1000 nm. By doing so, the light emitting device will emit light in a wavelength range, which is suitable for a broad variety of applications. According to a preferred embodiment of the present invention, the light that enters the conversion element is at least partly converted to light in the wavelength range of ≧350 nm and ≦880 nm, more preferably ≧380 nm and ≦780 nm.

According to a preferred embodiment of the invention, the conversion element comprises at least one exit surface, where light can exit the conversion element. In order to enhance this, according to a preferred embodiment of the present invention, the at least one exit surface is equipped with a refractive and/or diffractive structure or surface. This includes that the at least one exit surface is equipped with a scattering structure, a pyramid-like structure, a micro lens structure or a compound parabolic concentrator (CPC). The exit surface may contain one or a plurality of the indicated structures. The geometry of the exit structure can also be used to direct the emitted light from the exit surface to meet any requirement of an application.

According to a preferred embodiment of the invention, the at least one exit surface is optically directly coupled to a light guiding structure, by coupling the light conversion element to a light guide with a medium having an refractive index n_(c) close to the refractive index of either the conversion element n_(conv) or the light guide n_(g). The minimum of the difference of (abs(n_(c)−n_(conv)) and abs(n_(c)−n_(g)) is preferably <0.3, more preferably <0.1 and most preferably <0.01.

According to a preferred embodiment of the invention, each of the at least one entrance surfaces has an entrance surface area, the entrance surface areas being numbered A₁ . . . A_(n) and each of the at least one exit surfaces has an exit surface area, the exit surface areas being numbered E₁ . . . E_(n) and the sum of each of the at least one entrance surface areas A_(n) is A=A₁+A₂ . . . +A_(n) and the sum of each of the at least one exit surface areas E_(n) is E=E₁+E₂ . . . +E_(n) and the ratio A:E, A and E being as defined above, is ≧2:1 and ≦50000:1.

By doing so, the light flux of the LED can be set within the preferred and desired range. According to a preferred embodiment of the present invention, the ratio A:E, A and E being as defined above, is ≧5:1 and ≦5000:1, more preferably ≧10:1 and ≦3000:1 yet more preferably ≧20:1 and ≦1000:1, and most preferably ≧50:1 and ≦500:1.

According to a preferred embodiment of the invention, the at least one conversion element has an refractive index n of ≧1.5 and ≦3. By doing so, it can be easily achieved that the efficiency of the LED is within a desired range. Especially, by setting the refractive index as described, the light that enters the conversion element as described will undergo total reflection at the sides/surfaces of the conversion element, which are no exit surfaces. The fraction of the light from the LEDs which is emitted through the exit surface (possibly after conversion) of the conversion element compared to the total emitted light can be as high as

${1 - \frac{1}{2n^{2}}},$

with n being the refractive index of the conversion element. This results in a very highly efficient light-emitting device. Preferably the at least one conversion element has a refractive index n of ≧1.5 and ≦2.8, more preferably ≧1.7 and ≦2.6

According to a preferred embodiment of the present invention, the transmittance for emitted light of the conversion element is ≧8 and ≦1. This greatly enhances the efficiency of the light-emitting device. Preferably, the transmittance of the conversion element is ≧9 and ≦1, more preferably ≧0.95 and ≦1.

According to a preferred embodiment of the present invention, the relation of the quantum efficiency at a temperature T compared to the quantum efficiency at 20° C. (thermal quenching) of the conversion element is ≧70% and ≦100% at 100° C., preferably ≧80% and ≦100% at 100° C. and most preferably ≧90% and ≦100% at 100° C.

According to a preferred embodiment of the present invention, the temperature at which the quantum efficiency of the conversion layer is reduced to 50% compared to the quantum efficiency at room temperature, (=TQ_(50%)-value), is ≧120° C. and ≦300° C., preferably 150° C.≦TQ_(50%)≦350° C. and more preferably 180° C.≦TQ_(50%)≦400° C.

According to a preferred embodiment of the present invention, the light delivery device comprises at least one further auxiliary LED which emits in the wavelength of ≧220 nm to ≦600 nm.

By doing so, it is possible in most applications within the present invention to very easily shift the color temperature of the light provided by the light delivery device without lowering the original light flux.

According to a preferred embodiment of the present invention, the auxiliary LEDs have (combined) a power of 2% to 100% of the first LED. In case that more than one first LED is present, it is preferred that the auxiliary LEDs have (combined) a power of ≧10% to ≦1000% of the combined first LEDs.

According to a preferred embodiment of the present invention, the auxiliary LEDs are mounted either individually or in a die package on a single supporting plate serving as a heat conductor and providing the electrical contacts for operation. The one or more supporting plates may also contain active electronic elements for LED protection, operation and control. In addition, according to a preferred embodiment of the present invention the auxiliary LEDs on a supporting plate are covered with optical structures to optimise the light output of the auxiliary LEDs.

In a further preferred embodiment of the present invention, the auxiliary LEDs are mounted on a supporting plate with a packing density of ≧0.05 and ≦0.5, preferably ≧0.1 and ≦0.3. The packing density is the ratio of the sum of the LED die surface areas divided by the surface area of the supporting plate. By doing so, it is possible to realize a light emitting device with particularly high lumen flux and superior luminance at a high power efficiency, which is achieved by effective cooling of the auxiliary LEDs, keeping the junction temperature below the specified values of the auxiliary LEDs.

According to a preferred embodiment of the present invention, the light from the at least one first LED is sent to the at least one conversion element in a preferred first light propagation direction and the light sent from the auxiliary LEDs towards the at least one conversion element has an angle towards the preferred first light direction of ≧65° and ≦115°, preferably ≧75° and ≦105° and most preferably 85° and 95°.

In such an arrangement it is possible in most applications within the present invention to ensure that the light that is emitted by the auxiliary LEDs is only or essentially used for conversion inside the conversion element, thereby allowing to “add” light of a certain wavelength.

According to a preferred embodiment of the present invention, the auxiliary LEDs are placed inside a support tube.

Preferably the part of the support tube, where no auxiliary LEDs are placed, is preferably covered with a highly reflective coating, preferably a mirror or a dielectric coating or a mixture thereof. By doing so, the efficiency of the conversion element(s) and the light emitting device can be enhanced further. The mirror is preferably applied by sputtering or evaporation in vacuum directly on the at least one further surface which is neither an exit nor an entrance surface. The mirror material is preferably selected from a group comprising silver, aluminum and/or mixtures thereof. The thickness of the mirror is preferably ≧50 nm and ≦1000 nm.

In such an arrangement it is possible in most applications within the present invention to ensure that the light that is emitted by the auxiliary LEDs is only or essentially used for conversion inside the conversion element, thereby allowing to “add” light of a certain wavelength and lowering the power requirements of the LEDs.

According to a preferred embodiment of the invention, the glass phase ratio of the ceramic conversion material is ≧2% to ≦5%, according to an embodiment of the present invention, ≧3% to ≦4%. It has been shown in practice that materials with such a glass phase ratio show the improved characteristics, which are advantageous and desired for the present invention.

The term “glass phase” in the sense of the present invention means especially non-crystalline grain boundary phases, which may be detected by scanning electron microscopy or transmission electron microscopy.

According to a preferred embodiment of the present invention, the surface roughness RMS (disruption of the planarity of a surface; measured as the geometric mean of the difference between highest and deepest surface features) of the surface(s) of the ceramic conversion material and/or the conversion element(s) is ≧0.001 μm and ≦100 μm. According to one embodiment of the present invention, the surface roughness of the surface(s) of the ceramic conversion material and/or the conversion element(s) is ≧0.01 μm and ≦10 μm, according to another embodiment of the present invention≧0.1 μm and ≦5 μm, according to yet another embodiment of the present invention≧0.15 μm and ≦3 μm. and according to still another embodiment of the present invention≧0.2 μm and ≦2 μm.

According to a preferred embodiment of the present invention, the specific surface area of the ceramic conversion material and/or the conversion element(s) is ≧10⁻⁷ m²/g and ≦1 m²/g.

According to a preferred embodiment of the present invention, the ceramic conversion material is essentially made of material selected from the group of

(M^(I) _(1-x-y)M^(II) _(x)M^(III) _(y))₃(M^(IV) _(1-z)M^(V) _(z))₅O₁₂—where M^(I) is selected from the group comprising Y, Lu or mixtures thereof, M^(II) is selected from the group comprising Gd, La, Yb or mixtures thereof, M^(III) is selected from the group comprising Tb, Pr, Ce, Er, Nd, Eu or mixtures thereof, M^(IV) is Al, M^(V) is selected from the group comprising Ga, Sc or mixtures thereof, and 0≦x≦1, 0≦y≦0.1, 0≦z≦1,

(M^(I) _(1-x-y)M^(II) _(x)M^(III) _(y))₂O₃—where M^(I) is selected from the group comprising Y, Lu or mixtures thereof, M^(II) is selected from the group comprising Gd, La, Yb or mixtures thereof, M^(III) is selected from the group comprising Tb, Pr, Ce, Er, Nd, Eu, Bi, Sb or mixtures thereof, and 0≦x≦1, 0≦y≦0.1,

(M^(I) _(1-x-y)M^(II) _(x)M^(III) _(y))S_(1-z)Se_(z)—where M^(I) is selected from the group comprising Ca, Sr, Mg, Ba or mixtures thereof, M^(II) is selected from the group comprising Ce, Eu, Mn, Tb, Sm, Pr, Sb, Sn or mixtures thereof, M^(III) is selected from the group comprising K, Na, Li, Rb, Zn or mixtures thereof, and 0≦x≦0.01, 0≦y≦0.05, 0≦z≦1,

(M^(I) _(1-x-y)M^(II) _(x)M^(III) _(y))O—where M^(I) is selected from the group comprising Ca, Sr, Mg, Ba or mixtures thereof, M^(II) is selected from the group comprising Ce, Eu, Mn, Tb, Sm, Pr or mixtures thereof, M^(III) is selected from the group comprising K, Na, Li, Rb, Zn or mixtures thereof, and 0≦x≦0.1, 0≦y≦0.1,

(M^(I) _(2-x)M^(II) _(x)M^(III) ₂)O₇—where M^(I) is selected from the group comprising La, Y, Gd, Lu, Ba, Sr or mixtures thereof, M^(II) is selected from the group comprising Eu, Tb, Pr, Ce, Nd, Sm, Tm or mixtures thereof, M^(III) is selected from the group comprising Hf, Zr, Ti, Ta, Nb or mixtures thereof, and 0≦x≦1,

(M^(I) _(1-x)M^(II) _(x)M^(III) _(1-y)M^(IV) _(y))O₃—where M^(I) is selected from the group comprising Ba, Sr, Ca, La, Y, Gd, Lu or mixtures thereof, M^(II) is selected from the group comprising Eu, Tb, Pr, Ce, Nd, Sm, Tm or mixtures thereof, M^(III) is selected from the group comprising Hf, Zr, Ti, Ta, Nb or mixtures thereof, and M^(IV) is selected from the group comprising Al, Ga, Sc, Si or mixtures thereof, and 0≦x≦0.1, 0≦y≦0.1.

According to a preferred embodiment of the present invention, the conversion element comprises at least one further surface which is neither an exit nor an entrance surface and where at least one, preferably all of said further surface(s) are covered with a reflective coating, preferably a mirror or a dielectric coating or a mixture thereof. By doing so, the efficiency of the conversion element(s) and the light emitting device can be enhanced further. The mirror is preferably applied by sputtering or evaporation in vacuum directly on the at least one further surface, which is neither an exit nor an entrance surface. The mirror material is preferably selected from a group comprising silver, aluminum and/or mixtures thereof. The thickness of the mirror is preferably ≧50 nm and ≦1000 nm

A light emitting device according to the present invention may be of use in a wide variety of systems and/or applications, amongst them one or more of the following:

-   -   medical lighting application systems,     -   endoscopes     -   devices for photodynamic therapy

The aforementioned components, as well as the claimed components and the components to be used in accordance with the invention in the described embodiments, are not subject to any special exceptions with respect to their size, shape, material selection and technical concept such that the selection criteria known in the pertinent field can be applied without limitations.

Additional details, features, characteristics and advantages of the object of the invention are disclosed in the subclaims, figures, examples and the following description of the respective figures and examples—which in an exemplary fashion—show several preferred embodiments and examples of a light delivery device according to the invention, wherein:

FIG. 1 shows a very schematic cross-sectional partial view of a light delivery device according to a first embodiment of the present invention;

FIG. 2 shows a very schematic cross-sectional partial view of a light delivery device according to a first embodiment of the present invention;

FIG. 3 shows a schematic cross-sectional partial view of the embodiment of FIG. 1 along line IV-IV in FIG. 4

FIG. 4 shows a cross-sectional view of the conversion element of the light delivery device of FIGS. 1 and 3 along line II-II in FIG. 3

FIG. 5 shows a graph showing three emission spectra of a light delivery device according to a first example of the invention;

FIG. 6 shows an enlarged section of the graph of FIG. 5; and

FIG. 7 shows a graph showing three emission spectra of a light delivery device according to a second example.

FIG. 1 shows a very schematic cross-sectional partial view of a light delivery device 1 according to a first embodiment of the present invention. The light delivery device 1 comprises a first LED 20, a first converter substance 30, which projects light towards the conversion element 10 through a collector lens 60. From the conversion element 10, the light is then partially converted and projected towards the optical fibre 70. The optical fibre then may e.g. lead the light towards the tip of an endoscopy device (not shown in the Fig.).

In order to shift the color temperature of the LED, several auxiliary LEDs 40 are provided on a support tube 50; this part of the embodiment will be described in more detail in FIG. 3, which is an enlarged partial view of this part of the light delivery device.

As can be best seen from FIG. 1, the angle between the preferred light direction from the first LED (which in this embodiment is essentially horizontal) and the light sent out from the auxiliary LEDs (which in this embodiment is essentially vertical) is approximately 90°.

FIG. 2 shows a very schematic cross-sectional partial view of a light delivery device according to a first embodiment of the present invention. This second embodiment is identical with that of FIG. 1 except that a second conversion element 15 is present.

FIG. 3 shows a schematic cross-sectional partial view the embodiment of FIG. 1 along line IV-IV in FIG. 4.

FIG. 4 shows a cross-sectional view of the conversion element of the light delivery device of FIGS. 1 and 3 along line II-II in FIG. 3.

As can be seen from FIGS. 3 and 4, the conversion element 10 is somewhat cylindrical in shape and preferably matches the optical fibre 70. It is circumferentially surrounded by the support tube 50, which holds several sets of auxiliary LEDs 40. In this embodiment, four rows of auxiliary LEDs were used; however, it goes without saying that more (or less) auxiliary LEDs may be used, depending on the actual application. The inside surface of the support tube where no LEDs are located, is covered with a mirror.

Preferably, the auxiliary LEDs are arranged closely in groups, e.g. rows, leaving large contiguous areas of the supporting tube coated with a highly reflective coating. By doing so, the total amount of LED light absorbed by the conversion element is maximized.

The conversion element 10 has two entrance surfaces A₁, A₂ (A₂ being the “side” of the cylinder that projects towards the LED 20), resulting in an A being A₁+A₂. Since there is only one exit surface with an exit surface area E₁, the numeral E, being the sum of each of the at least one exit surface areas would simply be E=E₁. The ratio of A:E is set to be 10:1 and 10000:1; in this example A:E would be approximately 400:1. However, it should be noted, that the embodiment in FIGS. 3 and 4 is highly schematic and the ratio may be different for other applications.

The lighting device according to the invention is—in a merely exemplarily fashion—furthermore illustrated by the following examples together with the FIGS. 5 to 7:

FIG. 5 shows a graph showing three emission spectra of a light delivery device according to a first example of the invention, FIG. 6 shows a enlarged section of the graph of FIG. 5.

EXAMPLE I

In Example I, a light delivery device with the setting of FIG. 1 was used. The first LED (reference no. 20 in FIG. 1) was a InGaN LED with a peak emission at 462 nm, the first converter substance (reference no. 30 in FIG. 1) was a YAG:Ce ceramic material with the composition Y_((3-x-y))Gd_(x)Al₅O₁₂:Ce_(y) with x=0.3 and y=0.06.

The conversion element (reference no. 10 in FIG. 1) was Y₂O₃:Eu with a 7% Europium doping and a density of 5.029 g/cm³.

The light delivery device furthermore comprises two sets of auxiliary LEDs (reference no. 40 in FIG. 1), which are also InGaN LEDs. Each set of LEDs has a power of 100% of the first LED and a peak emission at 465 nm.

FIGS. 5 and 6 show the spectra of the light delivery device with the first LED only (“LED”), with one set of auxiliary LEDs switched on (“Aux1”) and with both sets of auxiliary LEDs switched on (“Aux2”).

The data of FIGS. 5 and 6 are listed in Table I

TABLE I LED Aux1 Aux2 380 0.00188 0.00238 0.00288 382 0.001739 0.002239 0.002739 384 0.000654 0.001154 0.001654 386 0.000711 0.001211 0.001711 388 0.001233 0.001733 0.002233 390 0.00117 0.00167 0.00217 392 0.000811 0.001311 0.001811 394 0.000946 0.001446 0.001946 396 0.000838 0.001338 0.001838 398 0.000623 0.001123 0.001623 400 0.001035 0.001535 0.002035 402 0.001292 0.001792 0.002292 404 0.00122 0.00172 0.00222 406 0.001175 0.001675 0.002175 408 0.001278 0.001778 0.002278 410 0.001367 0.001867 0.002367 412 0.00144 0.00194 0.00244 414 0.001532 0.002032 0.002532 416 0.001929 0.002429 0.002929 418 0.002528 0.003028 0.003528 420 0.003352 0.003852 0.004352 422 0.004891 0.005391 0.005891 424 0.006672 0.007172 0.007672 426 0.008475 0.008975 0.009475 428 0.011025 0.011525 0.012025 430 0.014129 0.014629 0.015129 432 0.01841 0.01891 0.01941 434 0.023055 0.023555 0.024055 436 0.027142 0.027642 0.028142 438 0.032944 0.033444 0.033944 440 0.040675 0.041175 0.041675 442 0.047448 0.047948 0.048448 444 0.057997 0.058497 0.058997 446 0.06568 0.06618 0.06668 448 0.076898 0.077398 0.077898 450 0.088318 0.088818 0.089318 452 0.097781 0.098281 0.098781 454 0.103529 0.104029 0.104529 456 0.107177 0.107677 0.108177 458 0.109494 0.109994 0.110494 460 0.110901 0.111401 0.111901 462 0.093512 0.094012 0.094512 464 0.078426 0.078926 0.079426 466 0.065164 0.066119 0.067074 468 0.068973 0.070108 0.071243 470 0.08761 0.08811 0.08861 472 0.096669 0.097169 0.097669 474 0.100671 0.101351 0.102031 476 0.098311 0.098811 0.099311 478 0.093635 0.094135 0.094635 480 0.088668 0.089168 0.089668 482 0.085616 0.086116 0.086616 484 0.083357 0.083857 0.084357 486 0.079624 0.080124 0.080624 488 0.073583 0.074083 0.074583 490 0.070694 0.071414 0.072134 492 0.068335 0.068835 0.069335 494 0.064839 0.065339 0.065839 496 0.063057 0.063557 0.064057 498 0.062375 0.062875 0.063375 500 0.062363 0.062993 0.063623 502 0.062725 0.06337 0.064015 504 0.063773 0.064273 0.064773 506 0.068184 0.070894 0.073604 508 0.072833 0.078278 0.083723 510 0.076638 0.079698 0.082758 512 0.080117 0.080647 0.081177 514 0.084271 0.085041 0.085811 516 0.088583 0.089083 0.089583 518 0.092116 0.092726 0.093336 520 0.096028 0.096528 0.097028 522 0.098354 0.098854 0.099354 524 0.095827 0.096327 0.096827 526 0.094712 0.095212 0.095712 528 0.093644 0.094144 0.094644 530 0.086809 0.087309 0.087809 532 0.079557 0.080057 0.080557 534 0.078023 0.083963 0.089903 536 0.081832 0.083412 0.084992 538 0.096771 0.099706 0.102641 540 0.107926 0.110741 0.113556 542 0.116971 0.117571 0.118171 544 0.121157 0.121782 0.122407 546 0.122688 0.123223 0.123758 548 0.122018 0.122573 0.123128 550 0.121649 0.122704 0.123759 552 0.121918 0.124548 0.127178 554 0.122846 0.125451 0.128056 556 0.123639 0.125474 0.127309 558 0.123114 0.123614 0.124114 560 0.122137 0.122637 0.123137 562 0.121608 0.122568 0.123528 564 0.120783 0.122688 0.124593 566 0.119735 0.12131 0.122885 568 0.118723 0.120298 0.121873 570 0.118546 0.120606 0.122666 572 0.116935 0.11762 0.118305 574 0.115054 0.115614 0.116174 576 0.113432 0.114262 0.115092 578 0.109946 0.111191 0.112436 580 0.107852 0.110017 0.112182 582 0.113155 0.13106 0.148965 584 0.110682 0.124317 0.137952 586 0.10715 0.11296 0.11877 588 0.120096 0.159521 0.198946 590 0.107076 0.118441 0.129806 592 0.106777 0.118612 0.130447 594 0.126511 0.186606 0.246701 596 0.106581 0.124741 0.142901 598 0.103291 0.118781 0.134271 600 0.112167 0.152797 0.193427 602 0.100955 0.120695 0.140435 604 0.094712 0.104957 0.115202 606 0.094031 0.107736 0.121441 608 0.094532 0.114652 0.134772 610 0.105648 0.156603 0.207558 612 0.299 0.799 1.299 614 0.175572 0.397937 0.60.620302 616 0.134533 0.268638 0.402743 618 0.088959 0.124684 0.160409 620 0.077779 0.093569 0.109359 622 0.074426 0.088086 0.101746 624 0.075279 0.096684 0.118089 626 0.074294 0.099299 0.124304 628 0.073762 0.103197 0.132632 630 0.073588 0.107703 0.141818 632 0.098097 0.193427 0.288757 634 0.060529 0.075204 0.089879 636 0.055331 0.062916 0.070501 638 0.052421 0.058256 0.064091 640 0.049973 0.054533 0.059093 642 0.047951 0.052381 0.056811 644 0.045942 0.050327 0.054712 646 0.044127 0.048317 0.052507 648 0.042124 0.045564 0.049004 650 0.040988 0.045618 0.050248 652 0.048088 0.072903 0.097718 654 0.039911 0.050101 0.060291 656 0.03537 0.038875 0.04238 658 0.034343 0.039013 0.043683 660 0.031902 0.034377 0.036852 662 0.031165 0.035045 0.038925 664 0.034241 0.048226 0.062211 666 0.02811 0.030955 0.0338 668 0.0265 0.0287 0.0309 670 0.025269 0.027384 0.029499 672 0.023972 0.026072 0.028172 674 0.02249 0.02391 0.02533 676 0.0213 0.022575 0.02385 678 0.020134 0.021254 0.022374 680 0.019324 0.020729 0.022134 682 0.01838 0.019505 0.02063 684 0.017914 0.019504 0.021094 686 0.017255 0.01919 0.021125 688 0.021362 0.034522 0.047682 690 0.017832 0.024502 0.031172 692 0.014795 0.01648 0.018165 694 0.017148 0.026443 0.035738 696 0.013255 0.015435 0.017615 698 0.0121 0.01304 0.01398 700 0.011542 0.012727 0.013912 702 0.011226 0.012981 0.014736 704 0.011728 0.015483 0.019238 706 0.013805 0.023045 0.032285 708 0.026806 0.066926 0.107046 710 0.029198 0.076303 0.123408 712 0.013137 0.024182 0.035227 714 0.018797 0.043992 0.069187 716 0.008111 0.009701 0.011291 718 0.00744 0.008405 0.00937 720 0.006897 0.007732 0.008567 722 0.006787 0.007587 0.008387 724 0.006289 0.006994 0.007699 726 0.005959 0.006624 0.007289 728 0.005447 0.006077 0.006707 730 0.005466 0.006141 0.006816 732 0.005346 0.005961 0.006576 734 0.004935 0.005435 0.005935 736 0.004677 0.005177 0.005677 738 0.004646 0.005146 0.005646 740 0.004793 0.005293 0.005793 742 0.004545 0.0056 0.006655 744 0.004599 0.006199 0.007799 746 0.003901 0.004401 0.004901 748 0.003995 0.00496 0.005925 750 0.003715 0.004215 0.004715 752 0.003625 0.004125 0.004625 754 0.003318 0.003818 0.004318 756 0.003133 0.003633 0.004133 758 0.003193 0.003693 0.004193 760 0.00308 0.00358 0.00408 762 0.003095 0.003595 0.004095 764 0.002751 0.003251 0.003751 766 0.002666 0.003166 0.003666 768 0.002573 0.003073 0.003573 770 0.002335 0.002835 0.003335 772 0.002312 0.002812 0.003312 774 0.001938 0.002438 0.002938 776 0.001862 0.002362 0.002862 778 0.001972 0.002472 0.002972 780 0.001951 0.002451 0.002951

Further data of Example I are given in Table II:

TABLE II LED Aux1 Aux2 CCT [K] 4491 3481 2865 Ra 80 88 85 uv 0.011 0.002 0.009 x 0.3662 0.4043 0.4331 Y 0.3923 0.3857 0.3807 LE [lmW] 343 334 327 R1 77.7 94.2 97 R2 89.4 99 92.1 R3 95.6 93.9 87.6 R4 72.6 88.4 94.7 R5 76.1 92.1 97 R6 85.8 93.2 80.9 R7 83.6 82.1 76.2 R8 57.2 61.9 56.5 R9 14.9 9.9 7.2 R10 73.8 96.1 88.9 R11 68.6 88 96.7 R12 57.3 79.8 76.2 R13 80.6 96.9 94.7 R14 97.4 98.8 96

It can be clearly seen that a shift of the color temperature over approx. 1600K is possible without any deterioration of the lighting properties, such as the color rendering index Ra of the light delivery device.

FIG. 7 shows a graph with three emission spectra of a light delivery device according to a second example of the invention.

EXAMPLE II

In Example II, a light delivery device with the setting of FIG. 1 was used. The first LED (reference no. 20 in FIG. 1) was an InGaN LED with a peak emission at 462 nm, the first converter substance (reference no. 30 in FIG. 1) was a YAG:Ce ceramic material with the composition Y_((3-x-y))Gd_(x)Al₅O₁₂:Ce_(y) with x=0.3 and y=0.06.

The conversion element on Example II is CaS:Eu with 0.1% Europium.

The light delivery device furthermore comprises two sets of auxiliary LEDs (reference no. 40 in FIG. 1), which are also InGaN LEDs emitting at 450 nm. Each set of LEDs has a “strength” of 50% of the first LED.

FIG. 7 shows the spectra of the light delivery device with the first LED only (“LED”), with one set of auxiliary LEDs switched on (“Aux1”) and with both sets of auxiliary LEDs switched on (“Aux2”).

The data of FIG. 7 are listed in Table III:

TABLE III LED Aux 1 Aux 2 380 0.002731 0.002811 0.002891 382 0.00246 0.00254 0.00262 384 0.002295 0.002375 0.002455 386 0.002183 0.002263 0.002343 388 0.0021 0.00218 0.00226 390 0.002063 0.002143 0.002223 392 0.001984 0.002064 0.002144 394 0.001932 0.002012 0.002092 396 0.001891 0.001971 0.002051 398 0.001885 0.001965 0.002045 400 0.001894 0.001974 0.002054 402 0.001904 0.001984 0.002064 404 0.001916 0.001996 0.002076 406 0.00201 0.00209 0.00217 408 0.002198 0.002278 0.002358 410 0.002487 0.002567 0.002647 412 0.00291 0.00299 0.00307 414 0.003532 0.003612 0.003692 416 0.004441 0.004521 0.004601 418 0.005643 0.005723 0.005803 420 0.007188 0.007268 0.007348 422 0.009126 0.009206 0.009286 424 0.011543 0.011623 0.011703 426 0.014461 0.014541 0.014621 428 0.017876 0.017956 0.018036 430 0.021857 0.021937 0.022017 432 0.026492 0.026572 0.026652 434 0.031853 0.031933 0.032013 436 0.037928 0.038008 0.038088 438 0.044757 0.044837 0.044917 440 0.052341 0.052421 0.052501 442 0.06054 0.06062 0.0607 444 0.069068 0.069148 0.069228 446 0.0776 0.07768 0.07776 448 0.085827 0.085907 0.085987 450 0.093335 0.093415 0.093495 452 0.099715 0.099795 0.099875 454 0.104735 0.104815 0.104895 456 0.108405 0.108485 0.108565 458 0.110776 0.110856 0.110936 460 0.111859 0.111939 0.112019 462 0.111729 0.111809 0.111889 464 0.110624 0.110704 0.110784 466 0.10875 0.10883 0.10891 468 0.106153 0.106233 0.106313 470 0.102863 0.102943 0.103023 472 0.099002 0.099082 0.099162 474 0.094808 0.094888 0.094968 476 0.090407 0.090487 0.090567 478 0.085859 0.085939 0.086019 480 0.081277 0.081357 0.081437 482 0.076808 0.076888 0.076968 484 0.072592 0.072672 0.072752 486 0.068674 0.068754 0.068834 488 0.06512 0.0652 0.06528 490 0.062011 0.062091 0.062171 492 0.059401 0.059481 0.059561 494 0.057342 0.057422 0.057502 496 0.055892 0.055972 0.056052 498 0.055102 0.055182 0.055262 500 0.054976 0.055056 0.055136 502 0.055448 0.055528 0.055608 504 0.056473 0.056553 0.056633 506 0.057981 0.058061 0.058141 508 0.059874 0.059954 0.060034 510 0.06208 0.06216 0.06224 512 0.064504 0.064584 0.064664 514 0.067104 0.067184 0.067264 516 0.069813 0.069893 0.069973 518 0.072572 0.072652 0.072732 520 0.075336 0.075416 0.075496 522 0.078019 0.078099 0.078179 524 0.08058 0.08066 0.08074 526 0.082985 0.083065 0.083145 528 0.085209 0.085289 0.085369 530 0.087237 0.087317 0.087397 532 0.089072 0.089152 0.089232 534 0.090731 0.090811 0.090891 536 0.092226 0.092306 0.092386 538 0.093548 0.093628 0.093708 540 0.094726 0.094806 0.094886 542 0.09578 0.09586 0.09594 544 0.0967 0.09678 0.09686 546 0.097504 0.097584 0.097664 548 0.098204 0.098284 0.098364 550 0.098803 0.098883 0.098963 552 0.099295 0.099375 0.099455 554 0.099666 0.099746 0.099826 556 0.099941 0.100021 0.100101 558 0.10014 0.100253 0.100366 560 0.100248 0.100352 0.100457 562 0.100278 0.100419 0.10056 564 0.100233 0.10041 0.100586 566 0.10013 0.100255 0.10038 568 0.099938 0.100226 0.100514 570 0.099644 0.099935 0.100225 572 0.099263 0.099655 0.100047 574 0.09881 0.099252 0.099693 576 0.098291 0.098948 0.099605 578 0.097708 0.09838 0.099052 580 0.097084 0.098111 0.099137 582 0.096427 0.097766 0.099105 584 0.095733 0.097249 0.098765 586 0.094989 0.096655 0.098321 588 0.094207 0.096499 0.098791 590 0.093417 0.096078 0.098739 592 0.092576 0.096145 0.099715 594 0.091684 0.095957 0.100231 596 0.090785 0.095981 0.101177 598 0.089914 0.09634 0.102765 600 0.089023 0.097329 0.105635 602 0.088138 0.097263 0.106389 604 0.087334 0.097683 0.108031 606 0.086558 0.099057 0.111555 608 0.08584 0.101103 0.116365 610 0.085138 0.102026 0.118914 612 0.084485 0.104488 0.12449 614 0.083873 0.107333 0.130793 616 0.08323 0.109446 0.135663 618 0.082661 0.113232 0.143802 620 0.082144 0.116123 0.150101 622 0.081627 0.118431 0.155235 624 0.08123 0.122007 0.162784 626 0.080804 0.124579 0.168354 628 0.08048 0.128565 0.176649 630 0.080106 0.132753 0.1854 632 0.079787 0.135032 0.190277 634 0.079415 0.140028 0.200642 636 0.078916 0.141712 0.204508 638 0.078449 0.145427 0.212405 640 0.077836 0.146472 0.215107 642 0.077139 0.150875 0.224611 644 0.076284 0.150698 0.225112 646 0.075289 0.150925 0.226561 648 0.074195 0.152055 0.229916 650 0.072828 0.150963 0.229098 652 0.071378 0.149344 0.227309 654 0.069852 0.149852 0.229852 656 0.068139 0.145939 0.223738 658 0.066397 0.143834 0.221272 660 0.064552 0.138972 0.213393 662 0.062615 0.136383 0.210151 664 0.060556 0.133304 0.206053 666 0.0584 0.129308 0.200216 668 0.056123 0.125063 0.194003 670 0.053743 0.120684 0.187625 672 0.05133 0.113789 0.176248 674 0.049083 0.108819 0.168556 676 0.046732 0.103957 0.161182 678 0.044451 0.097638 0.150824 680 0.042273 0.091529 0.140785 682 0.040124 0.086984 0.133844 684 0.038025 0.083943 0.129862 686 0.035843 0.076383 0.116923 688 0.033855 0.073202 0.112548 690 0.031863 0.068753 0.105643 692 0.029922 0.062992 0.096063 694 0.028121 0.059684 0.091248 696 0.026411 0.055107 0.083803 698 0.024817 0.0518 0.078783 700 0.023267 0.04813 0.072993 702 0.021803 0.044705 0.067606 704 0.020463 0.041375 0.062287 706 0.019186 0.038765 0.058343 708 0.017968 0.035719 0.05347 710 0.016772 0.033093 0.049414 712 0.015685 0.030275 0.044866 714 0.014667 0.029027 0.043387 716 0.013678 0.026584 0.039491 718 0.012728 0.02487 0.037012 720 0.011838 0.021897 0.031956 722 0.011087 0.020362 0.029638 724 0.010336 0.018908 0.02748 726 0.009658 0.017608 0.025558 728 0.00902 0.015997 0.022974 730 0.008502 0.014717 0.020931 732 0.007991 0.013938 0.019885 734 0.007478 0.012436 0.017395 736 0.007028 0.012045 0.017063 738 0.00659 0.010689 0.014789 740 0.006218 0.010233 0.014248 742 0.005813 0.009442 0.013072 744 0.005459 0.008447 0.011434 746 0.005142 0.007815 0.010488 748 0.004859 0.007119 0.009379 750 0.004616 0.007121 0.009627 752 0.004355 0.006159 0.007964 754 0.004116 0.006123 0.008129 756 0.003899 0.005788 0.007677 758 0.003704 0.005228 0.006752 760 0.003509 0.00523 0.006952 762 0.00331 0.004353 0.005396 764 0.003101 0.004161 0.005221 766 0.002911 0.003969 0.005027 768 0.002731 0.003769 0.004806 770 0.002567 0.003607 0.004647 772 0.002475 0.003363 0.004251 774 0.002384 0.003092 0.0038 776 0.002342 0.002933 0.003525 778 0.002329 0.002724 0.003118 780 0.002339 0.002902 0.003465

Further data of Example II are given in Table IV:

TABLE IV LED Aux1 Aux2 CCT [K] 4881 3895 3180 Ra 88 93 83 uv 0.004 0.008 0.016 x 0.3494 0.3788 0.4035 y 0.3632 0.3579 0.3535 LE [lm/W] 297 254 226 R1 86.3 92 78.4 R2 94.1 94.2 85 R3 96.4 96.1 97 R4 80.1 97.2 85.9 R5 83.8 93.4 79.5 R6 88.3 94.3 83 R7 90.9 96.4 92.4 R8 80.2 84.1 65 R9 50.1 58.2 16.2 R10 82.5 92.9 73 R11 76.5 97.7 84.7 R12 62.9 79.4 66.8 R13 88.6 92.1 78.6 R14 97.9 96.4 96.6

It can be clearly seen that a shift of the color temperature over approx. 1700K is possible without any deterioration in the lighting properties, such as the Ra of the light delivery device.

In both examples it is possible to simply “add” red light, i.e. the spectra in the wavelength range of 380 to 580 nm are more or less identical for “LED”, “Aux1” as well as “Aux2”.

It should be noted that in both examples the light flux even increases by switching on the LED groups Aux1 and Aux2. If a constant flux is required, the first LED may be dimmed when the Aux1 and Aux2 LEDs are switched on. In this case the color temperature will be decreased even further with the full power of the Aux1 and Aux2 LEDs added. It is evident that the light flux of all LEDs can be tuned to any desired value between the maximum power applicable to the LED package and zero. Power can be modified either by increasing and decreasing the DC voltage and current or by application of fast current and voltage pulses at a frequency>10 Hz and modifying the ratio of the on and off-time of the power.

The particular combinations of elements and features in the above detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this patent application and the patents/applications incorporated by reference are also expressly contemplated. As those skilled in the art will recognize, variations, modifications, and other implementations of what is described herein can occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the above description is by way of example only, and is not intended to be limiting. The invention's scope is defined in the following claims and the equivalents thereto. Furthermore, reference signs used in the description and claims do not limit the scope of the invention as claimed. 

1. A method of delivering light from a light delivery device, the light delivery device comprising: at least one LED, at least one auxiliary LED, and at least one conversion element placed in a path of light emitted by the at least one LED and by the at least one auxiliary LED, wherein the at least one conversion element wavelength converts at least part of the light from the at least one LED and the at least one conversion element comprises a ceramic conversion material; the method comprising: switching on the at least one LED, and changing the color temperature of the light from the light delivery device by switching on the at least one auxiliary LED.
 2. The method of claim 1 further comprising changing the color temperature of the light from the light delivery device without lowering light flux from the light delivery device.
 3. The method of claim 1 wherein changing the color temperature of the light from the light delivery device comprises shifting the color temperature toward red.
 4. The method of claim 1 wherein changing the color temperature of the light from the light delivery device comprises adding red light to a spectrum of light from the light delivery device.
 5. The method of claim 1 wherein changing the color temperature of the light from the light delivery device comprises changing the color temperature by at least 1600 K. 